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Environments 2017, 4(3), 48; https://doi.org/10.3390/environments4030048

Adsorption of Extracellular Polymeric Substances Derived from S. cerevisiae to Ceria Nanoparticles and the Effects on Their Colloidal Stability

1
Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-shi 819-0395, Japan
2
Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Tecnology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
3
Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
4
Geosciences Group, Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
These two authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 23 May 2017 / Revised: 3 July 2017 / Accepted: 7 July 2017 / Published: 11 July 2017
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Abstract

In order to understand the adsorption preferences of extracellular polymeric substances (EPS) components derived from fungus Saccharomyces cerevisiae on sparingly soluble CeO2 nanoparticles (CeNPs), the adsorption experiments of the EPS including organic matter with low molecular weight have been performed at pH 6.0 at room temperature (25 ± 1 °C). The subsequent effects of the coating on the dispersibility of CeNPs was systematically measured as a function of time and ionic strength ranging from 1 to 1000 mmol L−1. Among the EPS and other components, orthophosphate and saccharides preferentially adsorb onto CeNPs, and proteins are the only major N-compounds adsorbing onto the CeNP surfaces. Adsorption of orthophosphate resulted in a dramatic decrease in ζ potential to −40 mV at pH > 5, whereas the EPS adsorption suppressed the deviation of ζ potential within a narrow range (−20–+20 mV) at pHs ranging from 3 to 11. Critical aggregation concentrations (CAC) of an electrolyte (NaCl), inorganic orthophosphate, and EPS solutions are 0.01, 0.14, and 0.25 mol L−1, respectively, indicating that the EPS adsorption suppresses aggregation of CeNPs by the electrostatic repulsive forces derived from the adsorbed orthophosphate and the steric barrier formed by organic matter on the nanoparticle surfaces. Therefore, the EPS derived from fungus S. cerevisiae can potentially enhance colloidal dispersibility of CeNPs at circumneutral pH. View Full-Text
Keywords: EPS; ceria; adsorption; aggregation EPS; ceria; adsorption; aggregation
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Masaki, S.; Nakano, Y.; Ichiyoshi, K.; Kawamoto, K.; Takeda, A.; Ohnuki, T.; Hochella, Jr., M.F.; Utsunomiya, S. Adsorption of Extracellular Polymeric Substances Derived from S. cerevisiae to Ceria Nanoparticles and the Effects on Their Colloidal Stability. Environments 2017, 4, 48.

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